Sawflies on gooseberries and red currants
We have grown currants and gooseberries for many years, when it became OK to do so. This year, our gooseberry bushes have been stripped of leaves in three days, leaving just occasional major leaf veins sticking out. Having done a search, the culprit seems to be sawfly larvae. We find green larvae, from about 5 to 15 mm on the bushes, and not being able to get suitable treatments in time to do anything, we have been picking off the larvae a couple of times a day. The larvae have moved so fast that any treatment has missed the boat for this year. We are now concerned with ways to save the bushes, promoting recovery (we know we will get no crop next year), and how to prevent recurrence. We are proud to encourage pollinators and wildlife in general, so we are hoping for ideas that do not involve harsh broad-spectrum chemicals. Thank you for any suggestions.
Washtenaw County Michigan
Recovery of these plants should focus on two areas. First make sure the plants have good available water that is needed to help produce new buds and then to expand the leaves during the hot and often dry conditions of summer. Second stop any further feeding. If the plant is not flowering at the time the sawflies are feeding then pollinators are not an issue and you could use low toxicity materials like insecticidal soap and spray only these plants and avoid other flowering plants or spray very early in the morning when bees are not out. Another choice would be a bioinsecticide from the Neem plant called Azadirachtin. It is labeled for sawflies and since it must be ingested it is unlikely to bother bees since they are not feeding on the plant to ingest it. See David Smitley (MSU Entomologists) article on control of invasive pests: https://www.canr.msu.edu/news/how-to-control-invasive-pests-while-protecting-pollinators-and-other-beneficial-insects Sawflies can also be rinsed off plants with a strong stream of water. I used to do this on small pine that were attacked by a different type of sawfly.